Internal combustion engines, in particular gasoline engines with direct injection, generate fine particulate matter during engine operation that may be subject to emission standards. To enable emission compliance, gasoline particulate filters (GPFs) may be included in the engine exhaust, to trap particulate matter before releasing the exhaust to the atmosphere, wherein regeneration of the filter and filter functioning may be controlled and regularly assessed. Sometimes, the particulate filter may not be able to trap particulate matter due to degradation of the filter. In other circumstances, the filter may be missing or be removed from an exhaust system. In order to detect a degraded or missing GPF, one or more pressure sensors may be used for diagnosis and such sensors may be coupled upstream and/or downstream of the GPF.
As such, various types of pressure sensors have been developed for use that are configured to detect filter degradation and monitor filter performance. One example approach shown by Nieuwstadt in U.S. Pat. No. 6,947,831 discloses the use of a differential pressure sensor to determine the state of a particulate filter for regeneration purposes. By monitoring differential pressure across the filter and comparing it against a threshold, a filter regeneration may be performed or degradation of the filter may be diagnosed. Nieuwstadt also discloses that the differential pressure sensor could get degraded, resulting in erroneous determination that the filter itself has become degraded. Therein, a comparison of expected pressure response with actual pressure reading based to exhaust flow variation may be used to indicate pressure sensor degradation, and regeneration of the filter may be controlled accordingly.
However, the inventors herein have recognized potential issues with the above approaches. As one example, the downstream and/or upstream connections of the differential pressure sensor to the particulate filter in the exhaust system might become disconnected, resulting in inaccurate pressure readings. Additionally, in vehicle systems that include an exhaust tuning valve in addition to a differential pressure sensor, if the downstream hose connection between the particulate filter and differential pressure sensor becomes disconnected and the exhaust tuning valve is closed, a missing or a degraded particulate filter may be undetectable. With the exhaust tuning valve closed and the downstream hose disconnected or degraded, the increased exhaust backpressure resulting from the closure of the valve is sensed by the differential pressure sensor on the upstream hose-side of the differential pressure sensor, but the downstream hose-side of the differential pressure sensor senses atmospheric pressure. Thus, the differential pressure sensor may measure an increase in differential pressure when the exhaust tuning valve closes and the downstream hose is disconnected, even when the GPF is missing or degraded, which may mimic the pressure drop measured by the differential pressure sensor when an intact, non-degraded GPF is present.
In one example, the issues described above may be addressed by a method including indicating degradation of a hose coupled across a particulate filter responsive to a difference between a first differential pressure and a second differential pressure being greater than a threshold, the first differential pressure measured by a differential pressure sensor positioned in the hose responsive to a downstream exhaust tuning valve being fully open, the second differential pressure measured by the differential pressure sensor responsive to the exhaust tuning valve being fully closed.
In this way, GPF diagnostics may be performed with higher reliability and a distinction may be made between the degradation of particulate filter functioning versus the connection of the DP sensor that may have become disconnected during engine operation.
As one example, a first average differential pressure across the particulate filter may be measured with the differential pressure sensor during a first condition comprising operating the exhaust system with an exhaust tuning valve fully open. The exhaust tuning valve may be a valve positioned downstream in the exhaust system coupled across a muffler and that may act to control backpressure in the system and/or exhaust flow through the muffler. A second average differential pressure across the particulate filter may then be measured with the differential pressure sensor during a second condition comprising operating the exhaust system with the exhaust tuning valve fully closed. The calculated pressure difference between the first average differential pressure and the second average differential pressure in the exhaust system may be compared to a threshold value and used to infer degradation of the hose. In the event that hose degradation is not indicated, differential pressure measurement across the particulate filter may be compared directly to an expected pressure and if the measured pressure is different from the expected pressure, a degraded filter is inferred.
Thus, a degraded filter or a degraded hose connection of the DP sensor may be reliably determined and a distinction may be made between the degradation of particulate filter function and degradation of the downstream hose connection of the DP sensor. Overall, accuracy and reliability of diagnosing of an exhaust particulate filter is increased, while enabling higher emissions compliance.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.